US2267023A - Dowel for concrete pavements - Google Patents

Description

Dec. 23, 1941. w. s. GODWIN DOWEL FOR CONCRETE PAVEMENTS 3 Sheets-Sheet 1 Filed NOV. 10, 1937 M m, w

- Dec. 23, 1941. w. s. GODWIN 2,267,023

DOWEL FOR CONCRETE PAVEMENTS Filed Nov. 10, 1937 3 Sheets-Sheet 2 Dec. 23, 1941. w. s. GODW IN 2,267,023

' DOWEL FOR CONCRETE PAVEMENTS Filed Nov. 10, 1957 3 Sheets-Sheet 3 mm om Patented Dec. 23,1941

DOWEL FOB CONCRETE PAVEMENTS William S. Godwin, Baltimore, Md., assignor to W. 8. Godwin Company, Inc., a corporation of Maryland Application November 16, 1931, Serial No. 173,785

the maximum stresses are ordinarily applied in Claims.

To prevent cracking and injury to the road surface, concrete paving is made in sections, which are generally of standard length and width, and the joints between the adjacent sections are designed and constructed to provide for lateral contraction and expansion and for vertical warping of the edges due to changes of temperature and for yielding to the load, and change of level of the supporting bed or soil.

The use of dowels extending across the Joints and imbedded in the concrete below the road surface on both sides of the joints, and extending transversely to the adjacent edges, from one section to the other, to transmit the traffic loads across the joints, and to connect the bodies of concrete on the opposite sides of the joints to cause adjacent portions of the concrete to move in unison and maintain their horizontal relation, irrespective of the diflference in loads on the two sides of the joint, the yielding of the soil below this work. It is also to be noted that, while imbedding one end oi; the dowel in asphalt provides for slipping, the'use of the asphalt involves extra time and expense in laying the pavement,

and the expansion and contraction of the concrete in the direction of the road surface breaks the bond between the asphalt and the bar or dowel and in time it becomes loose at one end so that its load-transmitting eflect is reduced. Also, the round bars are'in proportion to the weight of metal very easily bent and transmit a comparatively slight degree of support across the the joint, and other conditions, is part of the.

established practice.

The present invention relates to a new and improved form of load-transmitting device or dowelfor this purpose, the term "dowel being used in the art to designate the prior constructions above suggested.

These dowels, as now constructed, are subject to a'number of dimculties, and it is the object of the present invention to reduce or overcome the various difiicultie's encountered in this connection. The dowels in most general use are in the form of bars of circular cross section about two feet long.- One end of each bar is molded in the concrete on one side of the joint and the other end is seated in asphalt imbedded in the concrete on the other side of the joint. The asphalt provides for slippage of the dowels as the concrete expands and contracts, the main function of the dowels being to support the concrete on either side of the joint from the concrete on the other side to maintain the horizontal relation of the concrete slabs and thus to compensate for diiTerences of loading or varia-' tion of support, warping of the edges, etc.; therefore the dowel acts as a cantilever and the main stress to which it is subjected is a transverse stress which, under certain circumstances as when the slab edges are very close together, may become mainly a shearing-stress.

The circular dowels are subject to the objection that the maximum transverse dimension is exceedingly large in proportion to the transverse strength of the bar, or dowel, particularly in a vertical direction which is the direction in which joint.

. In addition to the plain round bars, dowels have been provided which are anchored in concrete by increase of the horizontal dimension of the dowel at a location spaced inwardly within the body of the concrete from the edge surface of the concrete at the joint. This expansion of the dowel has the effect of weakening the concrete slab and creating a tendency to split in a plane parallel to the road surface when there is a sumcient difference in loading between the two sides of the joint, Also the extended horizontal dimension of such dowels interferes with the concrete and causes spaces or faults beneath the dowels.

The improved dowel is made in a plurality 'of parts imbedded in the concrete on opposite sides of the joint, and the dowel parts are operatively combined by telescoping or slip connections which retain the supporting effect 01 the dowel in all conditions of contraction and expansion of the joint in the pavement, permitting the dowel parts on the opposite sides of the joint to move relatively to each other in the direction of their length without disturbing their attachment to 1 the concrete; so that the respective parts of the dowel, being imbedded in the concrete as it is laid, are rigidly secured therein so that the maximum supporting eflect results and there is no variation throughout the life of the pavement in this supporting effect or force transmitted from one side of the joint to the other by the dowel. Y

It is also of importance that, the transverse cross section of both parts of the dowel being elongated in a vertical direction and being widely in excess of the horizontal transverse dimension of the cross section, theresistance to vertical stresses is largely increased in proportion to the area of the cross section; and the interferencewith the laying of the concrete, due to the excess maximum transverse horizontal dimension of v 7 many of the dowels in use, is overcome. The

dowel of the invention does not interfere in any way with the laying of the concrete. and leaves no fault or space in the concrete beneath the dowel in the completed pavement.

The invention also provides means for supporting and alining the dowels in horizontal relation prior to and during the pouring of the concrete. This provision is of great importance as, particularly with a dowel possessing a high degree of rigidity, disalinement may interfere with the operation of the sliding connection and even loosen the attachment of the dowel members in and to the concrete.

Owing to the vertical rigidity of the dowel of the invention, it is essential that it be alined with its length in parallelism with the road surface and that it retain its alinement throuzhthe pouring operation which often exerts a strong tendency to disturb the set-up of the dowels and fillers, the mixed concrete being deposited rapidly and in considerable quantities. To this end, the invention provides means for supporting and alining the dowels in parallelism to and with the top surfaces of the pavement prior to and during the pouring of the concrete.

The invention provides a load transfer assemlooking from the left in Figure 13.

bly or dowel which allows for all the natural movements of the concrete slabs, maintaining the horizontal relation of the adjacent edges of the slabs or sections and causing the slabs to move together with the change of loading, etc., does not interfere with the laying of the concrete, is cheap to construct, and presents the maximum support and resistance to bending of the dowel obtainable with any given cross-sectional area and weight of metal, and possesses other advantages which will hereafter more fully appear.

In the accompanying drawings, I have illustrated a dowel or load transfer device for joints in concrete pavements and the like, embodying the features of the invention in the preferred form.

In the drawings:

Figure 1 is a vertical section through an expansion joint of a concrete pavement, showing the improved dowel of the invention in elevation.

Figure 2 is a horizontal section taken on the line 2-2 in Figure 1.

Figure 3 is a vertical transverse section on the line 3-3 in Figure 1.

Figure 4 is a vertical transverse section on the line 4-4 in Figure 1.

Figure 5 is a transverse-section on the line 5-5 in Figure 1, illustrating the facility with which the concrete fills the area under the dowel, leaving no cavities or faults.

Figure 6 is a perspective view of the shank of the dowel prior to assembling and casting in the concrete.

Figure 7 is a similar view of the leg part of the dowel prior to assembling. v

Figure 8 shows a fragmentary sectionof joint filler adapted to be placed between the sections in forming the expansion joints.

Figure 9 is a similar view of a metal plate to be placed in the Joints ,between the concrete sections or slabs which are referred to as contrac-- tion joints.

Figure 10 is a section similar to Figure 1, showing the dowel in connection with the metal plate in a contraction joint.

Figure 11 is a top plan of a portion of concrete pavement showing the standard arrangement of the sections or slabs into which the pavement is divided, and the Joints between the edges of the slabs, the same being drawn to a very minute scale.

Figure 12 is a top plan view of a filler or filler strip showing the dowels and the dowel-supporting and alining means assembled prior to pouring.

Figure 13 is a fragmentary side elevation of the same looking from a direction at right angles to the length of the joint and from the right in Figure 14 Figure 14 is an end elevation of this structure,

Referring to the drawings by numerals, each of which is used to indicate the same or similar parts in the different figures, the construction shown comprises a concrete pavement i which is shown as an example of a standard construction, any arrangement of pavement which is formed in sections for the purposes stated or similar purposes being suitable to the appiication of the invention.

The practice illustrated in Figure 11 provides transverse expansion joints 2 spaced by intervals of feet, and between each two of these expansion joints there are illustrated two contraction joints 3, also transversely arranged. The practice illustrated also includes a longitudinal joint 4 extending the length of the pavement at the center. Thus, according to this arrangement, which is illustrated merely as an example of one application to road-building practice of the dowel of the invention, there are six concrete slabs or sections 5 between each pair of expansion joints 2, 2, and there are variations as to spacing and arrangement of pavement joints and spacing of dowels which need not be considered.

In accordance with the practice illustrated, the expansion joints 2, 2 are closed and filled by means of resilient filler plates or strips 8 to be further described; and the contraction joints 3, 4 contain and are supported by metal reinforcing plates 1 (see Figure 9). Both the fillers and plates are set up prior to pouring the concrete, so that they are cast in the concrete and may serve the purpose of molds between the slabs, forming the edges of the slabs in addition to serving the functions already described.

Referring now to Figures 1 to 7 and Figure 10, the dowel of the invention comprises two parts referred to herein as A and B connected by a telescoping connection C the respective elements of which are integral with parts A and B. More particularly, the part A in the preferred form illustrated consists of a shank 8 which is preferably commercial rolled steel bar of oblong or rectangular elongated cross section, the transverse dimension a: being, in the form shown, less than one-half of the long dimension Y which, in the installed position of the dowel, is upright; i. e., vertical or substantially so.

The shank 8, while it is most conveniently of rectangular cross section; may'of course be varied from this standard shape without departure from the theory of the invention, other standard shapes being available. Spaced from the end of the shank a suflicient distance to provide a satisfactory male portion 9 of the telescoping connection 0 to be described, I have shown a transverse flange I ll which, in the form illustrated, is a separate apertured plate welded in position and extending outwardly from' the shank 8 radially in all directions, the shank being most conveniently passed through the plate to the desired relation of the parts. This flange I0 19M as. rectangular and symmetrical in it 'flllers 6 and plates 1 with the dowels in assemj relation to the transverse section of the shank 8, the size and proportions oi the flange "I not being critical. I

At the end or the shank 8 adjacent the plate I there is a take-up screw ll projecting in the direction of the length of the shank and provided with a thumb nut l2. Any other suitable take-up may be employed at the end of male portion 9.

The part B of the dowel, as shown, consists of two legs I and I! which are shown in the form oi steel bars arranged in parallel and secured together in any suitable manner, the construction illustrated and to be described being preierred, and an important feature being that the part B is connected tothe part A by a telescoping or slip connection C.

The legs I! and I5, as shown, are oi! oblong dimensions of the transverse cross section of the shank 8. These dimensions are given as descriptive of one example only of the construction and are capable of variation, as .is also the cross section shown, there being various known equivalents of the solid oblong shape.

The legs l6 and I5 are in the form of the invention shown secured together by sheet metal cover plates l8 and I1 which-span the bars or legs l4 and I5, extending from one to the other on each side, being welded as illustrated at l8 or otherwise secured thereto. These cover plates are shown as turned outwardly at their ends l9 and 20 which are adjacent the ends of the bars or legs l4 and I5, adjacent flange In in the assembled relation. J I

The turned ends l9 and 20, as shown, are substantially at right angles to the length of the bars l4 and I5, so that in the assembled rela- 4 tion of the dowel as hereinafter described these ends or flanges I9 and 20 are parallel to the flange ID of the part A. The plates l6 and ll are shown as reduced at their rear ends near the center of the length of the bars I4 and I5 and turned inwardly at 20 between the bars, in which position they may be welded together if desired to strengthen the structure, and welded to the adjacent surfaces of bars It and I5. Holes H are shown for screws ll.

Referring to Figure 3, it will be noted that the plates l6 and I1 form the sides of the tubular portion or socket 22 of the telescoping connection C, the bars or legs l4 and forming the top andbottom walls of this tubular portion or socket 22 which receives and fits the projecting end of member A, at 9.

In the use of the dowel, the parts A and B thereof are assembled withthe joint filler 6 in the expansion joints and with the metalplates l in the contraction joints, as illustrated in Figures 1, 2, and 10, respectively. The filler 6 and bled relation thereto in molding position on the bed.

Referring to Figures 1 and 2, the end 9 of each dowel is passed through suitable apertures 2' in the flller 6, bringing the dance l0 into contact with one side of the flller 8. The part B of the dowel is then advanced into the position in which the projecting portion 9 of shank I enters the tubular socket 22, the screw being passed through the opening II in the end of the socket at 2|. The nut I2 is then engaged .with the take-up screw II and tightened, closing the telescoping joint 0 and holding the flanges I9 and 20 in close contact with the flller strip 6 opposite to the flange II. The flanges and take-up screws serve to secure the dowel to the flller to support the dowel during the pouring of the concrete. subsequent failure of the screw is not material. Various means for supporting the flller 8 during pouring are provided.

The operation of assembling the joint in connection with'the metal plates 1 similar to that in connection with the expa'nsii n filler strip 6, except that the plates 1 are thiniier than filler 6 and hence the flanges I0, I 9, and 20 are more closely related when the telescoping joint 0 is closed.

' Figure 5, which shows the improved dowel when ready for the pouring oi the concrete, illustrates the fact that due to the relatively small laterc. dimension of the cross section of the shank 8, the same being true of the legs H and Hi, there is no tendency on the part of the concrete to form a fault or cavity at 24 directly beneath the shank or legs or, collectively speaking, the bars 8, l4, and [5; an important point being -.that the horizontal dimension 4, 6' of the transversecross section of each bar 8, I 4, and I5, is extremely small in proportion to the transverse strength of the dowel, whereby the concrete is freely admitted beneath the dowel in pouring. This feature is also of importance in connection with the tendency of concrete slabs to crack or split horizontally when the inserts at the jointsare of considerable horizontal area.

In addition to the advantage in pouring, the construction illustrated has the important further advantage that it can be made at small cost from plain rolled bars of standard cross section, either oblong, rectangular, or other suitable standard shape, it being important that the transverse cross section be elongated in one direction to be placed in upright position. It

is also of importance that the telescoping conaccordance with the old practice, making it on the other hand entirely convenient and feasible to have both parts of the dowel cast and rigidly imbedded in the body of the concrete so that plates I are suitably supported upon the bed on with the combination of the rigid attachment of particularly with the dowel of the invention on account of the rigidity of this dowel in vertical direction, reference being had to the operative position of the dowel, that when set up prior to pouring-the dowels be alined or disposed with the length of the dowel parallel to the road surface or pavement surface and at right angles to the length of the joint between the concrete slabs, and that the dowels maintain this position throughout the. pouring operation. In this way, the dowels are cast in the concrete with their length in substantially exact parallelism with the road surface so that as the slabs or sections contract and expand the sliding connection between the parts of the dowel will work freely without unnecessary lateral stress. To this end, the invention provides supporting and alining means for the dowel, shown in Figures 12, 13. and 14' with the dowels assembled for pouring. These figures show the joint illustrated in Figures 1 to 4, though this supporting and alining device is equally applicable to the joint shown in Figure 10.

- The construction illustrated includes base supports 25 and 28 shown in the form of inverted channel irons resting on and having their flanges 2'l imbedded in the subsoil 28 beneath the pavement, it being understood that almost any beamshape may be used for this purpose, the channel being preferred; These base members 25 and 2i are laid parallel to the pavement joint and parallel to the filler 6 or plate I, and are located they are suitably shouldered at 34 to engage washers 35, or otherwise provided with suitable flanges or shoulders at this point to rest on the top surface of the corresponding base members 23 and 21. The lower ends 36 of, said struts are suitably threaded to receive nuts 31 which engage the under surfaces of the channel webs 38,

it being understood that the channels are provided with perforations 39 suitably spaced in accordance with any desired spacing of the dowels and adapted to receive the ends of the struts 3| and 32.

The channels or other bases 25 and 26 may be of any suitable length, either extending continuously the entire length of the Joint or provided in shorter lengths, joined, overlapped, or spaced at their ends as the circumstances may dictate.

The manner of assembling will be understood from the description of the construction, it being of primary importance that the dowels when assembled be so supported that they will not be disturbed and thrown out of position in the pooring of the concrete and so that they will be cast in the concrete in proper alinement. In the assembling operation, the dowels may be mounted on the fillers 6 or filler plates I, as first described in connection with Figures 1 to 4 and Figure 11, and assembled with the bases 25 and 26 by merely passing the struts 3| and 32 at their lower ends through the apertures 39 in the base-supporting members 25 and 28, threading the nuts 31 on to the lower ends of the struts 3| and 32 and tightening them in position. After this, the assembly, being substantially in place,

aromas may be finally located, whereby on pouring the concrete it is embodied in the Joint between the adjacent slabs.

The struts 3| and 32 or other uprights should be of a suitable length to locate and support and aline the dowel in parallelism with the top surface of the pavement and in parallelism with its length, so that there may be no harmful departure of the dowel from alinement with the road surface and-the length of the pavement. when thus supported, the dowel assembly (including the dowels, filler, and uprights) is cast in this position, whereby the dowels are retained in proper alinement so that there can be no undue resistence to the motion of the telescoping or yielding connection between the dowel parts as the concrete expands and contracts, and the-- -What I claim as new and desire to secure by Letters Patent is:

1. An expansion joint assembly for sectional concrete pavements, comprising a filler strip member adapted to be located within the narrow opening between the vertical edges of the said sections, rectangular elongated dowels extending through said filler strip at spaced intervals having their long cross-sectional dimensions perpendicular to the upper surface of the pavement, said dowels being adapted to have one end thereof imbedded in and adjacent the edge of one of the said concrete sections, elongated rectangular bars of substantially the same width as the said dowels imbedded adjacent the edge of an adjoining concrete section and extending parallel to the said dowel and positioned to provide sliding surfaces for the upper and lower horizontal faces of the opposite ends of the dowels, closure plates secured to the said bars to form rigid sockets for keeping the said dowels and bar members in alignment, the dowels being spaced from the rear end of the sockets to permit a limited movement of the dowels in and out of the socket members.

2. An expansion Joint assembly for sectional sections, rectangular elongated dowels extending through said flller strip at spaced intervals having their long cross-sectional dimensions perpendicular to the upper surface of the pavement, flange members positioned about the said dowels and on each side of the said strip member for locating the said strip relative to the said dowels, said dowels being adapted to have one end thereof imbedded and adjacent the edge of one of the said concrete sections, rectangular elongated bars of substantially the same width as the said dowels imbeddedadjacent the edge of an adjoining concrete section and extending parallel'to the said dowel and positioned to provide sliding surfaces for the upper and lower horizontal faces of the opposite ends of the spaced from the rear end of the sockets to permit a limited movement of the dowels in and out of the socket members and means for temporarily retaining the said dowels and bar members in said relationship.

3. An expansion joint assembly for sectional concrete pavements, comprising a filler strip member adapted to be located within the narrow opening between the vertical edges of the said sections, rectangular elongated dowels extending through said filler strip at spaced intervals having their long cross-sectional dimensions perpendicular to the upper surface of the pavements, flange members positioned about the said dowels and on each side of the said strip member for locating the said strip relative to the said dowels, said dowels being adapted to have one end thereof imbedded and adjacent the edge of one of the said concrete sections, rectangular elongated bars of substantially the same width as the said dowels imbedded adjacent the edge of an adjoining concrete section and extending parallel to the said dowels and positioned to provide sliding surfaces for the upper and lower horizontal faces of the opposite 4. In a sectional concrete pavement joint, comprising an elongated rectangular dowel, the dowel being adapted to have one end imbedded in the concrete on one side of the joint with its long cross sectional dimension perpendicular to the upper surface of the said pavement, a cooperating rectangular socket adapted to receive the opposite end of the said dowel in sliding and supporting relations, said socket comprising bar members of substantially the same width as the said dowel and positioned to form the horizontal sides of the said socket and closure plates secured to the bars to form the vertical side walls of the said socket, the end of the dowel received by the said socket being spaced outwardly from the rear end thereof. to permit a limited movement of the dowel in and out of the socket member.

5. In a sectional concrete pavement joint, comprising an elongated rectangular dowel, the dowel being adapted to have one end imbedded in the concrete on one side of the joint with its long cross sectional dimension perpendicular to the upper surface of the said pavement, a cooperating rectangular socket adapted to receive the opposite end of the said dowel in sliding and supporting relations, the horizontal side walls of the said socket being of greater thickness than the said vertical side walls and extending outwardly beyond the rear end of the said vertical walls, the end of the dowel received by the said socket being spaced outwardly from the rear end thereof to permit a limited movement of the dowel in and out of the socket member.

WILLIAM S. GODWIN.

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